In the electronic art generally, and particularly in the automatic control and instrumentation art, a variety of known electronic function generators accept signals representing values of real or simulated variables and provide outputs therefrom which are arbitrary, sometimes complicated functions of the variable. It is then often convenient to approximate such functions by piecewise - linear approximation. Prior art function generators of this type have included the diode-resistor, digital, and nonlinear resistor methods to accomplish the approximation. However, diode resistor methods require a great number of diodes and associated circuits to obtain the function and the breakpoints are not electronically or independently programmable; digital methods are usually expensive as analog to digital and digital to analog converters must be used with a digital processor (computer); and nonlinear resistor methods rely on the voltage/current characteristic of a non-linear resistor and such a characteristic cannot readily be produced. Other prior art programmable function generators have included current ladders for sequentially actuating a plurality of output transistors such as, for example, the programmable function generator of U.S. Pat. No. 3,740,539. Such schemes usually modulate a standard current which is applied to a resistor network that carries programmed information, hence additional processes.